1. Field of the Invention
The present invention relates to regulators for underwater breathing apparatus and more particularly to a scuba regulator second stage using pilot valve controlled pneumatic amplification.
2. Description of the Prior Art
In a typical self-contained underwater breathing apparatus (scuba), air or other breathable gas is supplied to a diver from a high pressure tank via a two-stage regulator. The regulator first stage is mounted at the supply tank and functions to reduce the air pressure to about 140 psi above the ambient pressure. Generally the tank and regulator first stage are supported on the diver's back. A conduit or hose supplies the reduced pressure air to a regulator second stage at the diver's mouthpiece. The second stage includes a demand valve system which opens to supply breathable gas in response to the inhalation effort of the diver. Provision is made to exhaust exhaled gas through the mouthpiece.
The use of pneumatic amplification in a scuba regular second stage is desirable to achieve very low inhalation effort. One such regulator is disclosed in the inventor's U.S. Pat. No. 4,076,041, issued Feb. 28, 1978 entitled PILOT VALVE OPERATED DEMAND REGULATOR FOR A BREATHING APPARATUS. Advantageously, but not necessarily, that regulator may be used in conjunction with a diaphragm having a variable effective sensing area, of the type shown in the inventor's U.S. Pat. No. 4,147,176, issued Apr. 3, 1979 entitled DIAPHRAGM ASSEMBLY FOR THE DEMAND REGULATOR OF A BREATHING APPARATUS. The diaphragm and regulator advantageously are linked by a mechanism of the type shown in the inventor's U.S. Pat. No. 4,029,120, issued June 14, 1977 entitled LINKAGE FOR THE DEMAND REGULATOR OF A BREATHING APPARATUS.
A regulator of the type utilizing these teachings has been found to achieve very low inhalation effort. That is, the diver can essentially inhale normally under water, and the regulator will respond to establish the proper flow of breathable gas. Unlike regulators which do not use pneumatic amplification, it is not necessary for the diver to use excessive inhalation force (i.e., to take a "deeper" breath than normal) to ensure opening of the valve.
However, the mechanism in the inventor's above mentioned patents were found to have certain features which merited improvement, and an object of the present invention is to facilitate such improvements.
For example, the pneumatic amplification valve shown in U.S. Pat. No. 4,076,041 could not be removed from its case intact, whereas it is an object of the present invention to provide a regulator in which the entire pilot and poppet valve mechanism can be removed from the case as a unitary assembly.
The poppet valve depicted in the U.S. Pat. No. 4,076,041 had some tendency to tilt when open. This was a possible source of instability. A further object of the present invention is to provide an assembly in which the poppet cannot tilt when either open or closed. Further, in the design shown in the U.S. Pat. No. 4,076,041 an unbalanced pressure condition could exist in the pilot control chamber, resulting in possible improper opening of the pilot valve. Yet another object of the present invention is to provide a regulator having a control chamber with balanced pressure so as to overcome this problem. These two improvements eliminate potential instability sources in the regulator.
Another objective of the present invention is to provide a simplified adjustment feature for the regulator linkage. In addition, another objective is to provide a simplified diaphragm mounting and linkage assembly.
Still another objective of the present invention is to provide a scuba regulator second stage in which the air supply hose inlet is situated immediately adjacent to the mouthpiece. This arrangement minimizes the torque force exerted on the regulator by the supply hose as the diver moves his head. Accordingly, using the present regulator, the diver is afforded more freedom of head motion without the risk of the regulator being pulled from his mouth by the torque force of the hose as the diver turns his head.